<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <h1>首页</h1>
    <script>
        var xhr = new XMLHttpRequest();

        // xhr.open('get', 'http://localhost:8888/ajax');
        xhr.open('get', 'http://localhost:9999/ajax');
        xhr.send(null);

        xhr.onreadystatechange =  () => {
            if (xhr.readyState == 4 && xhr.status == 200) {
               let r = xhr.responseText;
               console.log(r);     
            }
        }
    </script>
</body>
</html>